Aggregation/disaggregation of chlorophyll a in model phospholipid-detergent vesicles and micelles.

The photosynthetic pigments of higher plants exist in complex oligomeric states, which are difficult to study in vivo. To investigate aggregation processes of chlorophyll a (Chl a), we used an in vitro reconstitution procedure, with this pigment incorporated into liposomes of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), micelles and pre-micelle media of the detergent n-dodecyltrimethylammonium chloride (DTAC), and mixed, spontaneous, DMPC-DTAC vesicles and micelles. Chl a oligomers were characterized by UV-visible absorption, steady-state and time-resolved fluorescence, and fluorescence lifetime imaging microscopy.

Spontaneous vesicles, disks, threadlike and spherical micelles found in the solubilization of DMPC liposomes by the detergent DTAC.

The spontaneous colloidal nanostructures formed in water by the zwitterionic phospholipid DMPC (1,2-dimyristoyl-sn-glycero-3-phosphocholine) with the cationic detergent DTAC (n-dodecyltrimethylammonium chloride) were investigated at a fixed DMPC concentration and variable detergent:lipid total molar ratios (D:L). Apparent (neutral-sphere-equivalent) hydrodynamic diameters (Φ(e)) of liposomes and micelles were obtained by dynamic light scattering (DLS). Fluorescence lifetime imaging microscopy (FLIM), using chlorophyll-a as a probe, showed the morphology of giant vesicles and threadlike micelles.

Clinical and therapeutic characterization of a Portuguese sample of patients with schizophrenia.

Introduction: The development of Mental Health policies for psychiatric disorders should be driven by a correct knowledge of the socio-demographic, clinical and therapeutic realities of the disease. There is paucity of detailed studies in the Portuguese population that does not allow a direct comparation with other European countries. The objective of the present study is to characterize the sociodemograhic and clinical characteristics of schizophrenia patients in Portugal and the therapeutic patterns.

Time evolution of the thermotropic behavior of spontaneous liposomes and disks of the DMPC-DTAC aqueous system.

In this work, solubilization of the phospholipid 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) by the cationic detergent n-dodecyltrimethylammonium chloride (DTAC) was studied in aqueous solution, at a fixed DMPC concentration and variable detergent:lipid (D:L) molar ratios. The colloidal nanostructures present in different stages of the solubilization process were characterized using micro-differential scanning calorimetry (DSC) and dynamic light scattering (DLS) techniques. For total (analytical) D:L molar ratios below approximately 1, DTAC monomers incorporate into the DMPC liposome bilayers, forming smaller and more fluid vesicles than pure DMPC liposomes.

Unfolding kinetics of beta-lactoglobulin induced by surfactant and denaturant: a stopped-flow/fluorescence study.

The beta-->alpha transition of beta-lactoglobulin, a globular protein abundant in the milk of several mammals, is investigated in this work. This transition, induced by the cationic surfactant dodecyltrimethylammonium chloride (DTAC), is accompanied by partial unfolding of the protein. In this work, unfolding of bovine beta-lactoglobulin in DTAC is compared with its unfolding induced by the chemical denaturant guanidine hydrochloride (GnHCl).

Conformational transitions in beta-lactoglobulin induced by cationic amphiphiles: equilibrium studies.

The conformational transition from the native state in water ("beta-state") to a state containing a considerable amount of alpha-helices ("alpha-state") was studied for the protein beta-lactoglobulin (BLG), from bovine milk, in several colloidal solutions containing mixed micelles or spontaneous vesicles. These aggregates were formed in the bicationic system containing the surfactant dodecyltrimethylammonium chloride (DTAC) and the lipid didodecyldimethylammonium bromide (DDAB). The beta-->alpha transition in BLG, investigated by far-ultraviolet circular dichroism spectroscopy, is induced to the same protein alpha-state by pure and mixed DDAB/DTAC micelles or vesicles.

Conformational changes of beta-lactoglobulin in sodium bis(2-ethylhexyl) sulfosuccinate reverse micelles. A fluorescence and CD study.

The effect of beta-lactoglobulin encapsulation in sodium bis(2-ethylhexyl) sulfosuccinate reverse micelles on the environment of protein and on Trp was analysed at different water contents (omega0). CD data underlined the distortion of the beta-sheet and a less constrained tertiary structure as the omega0 increased, in agreement with a concomitant red shift and a decrease in the signal intensity obtained in steady-state fluorescence measurements. Fluorescence lifetimes, evaluated by biexponential analysis, were tau1 = 1.